/// <summary>
/// Advances the HashTable to new values without creating a complete packetCRC
/// DO NOT call this for an outgoing packet if you have already called "CreatePacketCRC"
/// You would advance hashtable twice.
/// This simply is a low cost variant for sniffed packets and advancing a mirrored/selfcreated hashtable in background.
/// </summary>
public void AdvanceHashTable()
{
// Construct/iterate to new HashMap (see disassembly for formula)
LastHashTable = CurrentHashTable;
CurrentHashTable.HASH1 = ((CurrentHashTable.HASH1 * CONST1) + CONST2) % CONST3;
CurrentHashTable.HASH2 = ((CurrentHashTable.HASH2 * CONST1) + CONST2) % CONST3;
CurrentHashTable.HASH3 = ((CurrentHashTable.HASH3 * CONST1) + CONST2) % CONST3;
CurrentHashTable.HASH4 = ((CurrentHashTable.HASH4 * CONST1) + CONST2) % CONST3;
CurrentHashTable.HASH5 = ((CurrentHashTable.HASH5 * CONST1) + CONST2) % CONST3;
}
/// <summary>
/// Sets (and returns) a valid CRC on a GameMessage (and advances the hash if not in testmode).
/// </summary>
/// <param name="Message">Message to set CRC in header</param>
/// <param name="BodyCRC">The plain CRC32</param>
/// <param name="TestMode">If set to false, hash is not iterated</param>
/// <returns>Shortened and encoded CRC also set on Message</returns>
public ushort CreatePacketCRC(GameMessage Message, out ushort BodyCRC, bool TestMode = false)
{
// create a generic CRC32 of message body
uint crc32 = Crc32.Compute(Message.BodyBytes);
// use first 2 bytes only
BodyCRC = (ushort)crc32;
// iterate hash
HashTable newHashTable = new HashTable();
newHashTable.HASH1 = ((CurrentHashTable.HASH1 * CONST1) + CONST2) % CONST3;
newHashTable.HASH2 = ((CurrentHashTable.HASH2 * CONST1) + CONST2) % CONST3;
newHashTable.HASH3 = ((CurrentHashTable.HASH3 * CONST1) + CONST2) % CONST3;
newHashTable.HASH4 = ((CurrentHashTable.HASH4 * CONST1) + CONST2) % CONST3;
newHashTable.HASH5 = ((CurrentHashTable.HASH5 * CONST1) + CONST2) % CONST3;
uint ptr = newHashTable.HASH5 & 3;
// select the right part to use
uint HashToUse = 0;
if (ptr == 0) HashToUse = newHashTable.HASH1;
else if (ptr == 1) HashToUse = newHashTable.HASH2;
else if (ptr == 2) HashToUse = newHashTable.HASH3;
else if (ptr == 3) HashToUse = newHashTable.HASH4;
else if (ptr == 4) HashToUse = newHashTable.HASH5;
// do encryption of plain CRC32
ushort shiftedPI = (ushort)((sbyte)Message.PI << 4);
uint packetCRC = HashToUse ^ shiftedPI ^ Message.BodyLength ^ BodyCRC;
// set encoded and shortened CRC on message
Message.HeaderCRC = (ushort)packetCRC;
// write back new Hashtable if not testMode
if (!TestMode)
{
LastHashTable = CurrentHashTable;
CurrentHashTable = newHashTable;
}
return Message.HeaderCRC;
}
public GetChoiceMessage(HashTable HashTable)
: base(MessageTypeLoginMode.GetChoice)
{
this.HashTable = HashTable;
}